Numerical simulation, formation of microstructure and mechanical properties of nanocopper prepared by severe plastic deformation

The development of the nanostructure in commercial pure copper, the strength and ductility as well as fracture micromechanisms after severe plastic deformation (SPD) with the technology of equal channel angular pressing (ECAP) are analysed. Experimental results and analyses showed that both strength and ductility can be increased simultaneously by SPD. The final grain size decreased from the initial 50 μm by SPD to 100–300 nm after ten passes. An increase of the ductility together with an increase of strength caused by SPD is explained by a strong grain refinement and by a dynamic equilibrium of weakening and strengthening and it is visible on the final static tensile test stress-strain charts. The fracture micromechanism is influenced by the number of ECAP passes. Transcrystalline ductile fracture took place in the range from one to 14 passes, whereas mixed fracture (transcrystalline ductile fracture with intercrystalline facets) occurred after 15 and 16 ECAP passes. Probable reasons of different fracture mechanisms are explained. Mathematical simulations of the ECAP were realised in software product DEFORM based on the finite element method (FEM).